1. Field of the Invention
This invention relates to a low cost, fuse and filter combination, a portion of which may be located exterior to an electrical or electromechanical device (e.g. an electric motor), so as to block undesirable electromagnetic noise signals and be less susceptible to the adverse effects of heat being produced as a consequence of the operation of the device.
2. Prior Art
As will be known to those skilled in the art, various electrical and electromechanical devices, such as, for example, an electric motor, an alternator, a solenoid, a magnetic clutch, a heater motor, and the like devices, which are commonly associated with either of the engine of a motor vehicle or a household appliance, undesirably generate spurious electromagnetic noise signals. More particularly, current fluctuations in the electrical system of a motor vehicle sometimes cause corresponding electromagnetic energy to be conducted through the wiring harness to be radiated therefrom as electromagnetic noise. Such noise signals frequently interfere with the reception of certain radio frequencies, so that a radio program may consequently become inaudible to the passengers in the motor vehicle. What is more, the operation of many household appliances also produces noise signals that are known to cause interference with the reception of radio and television signals in the home. Accordingly, various filter embodiments, including noise suppression capacitors or condensers, have been employed in an attempt to eliminate the electromagnetic effects of the noise signals. However, and as a result of the non-integral (i.e. add-on) relationship of the filter to the device as well as the relatively high cost of filter fabrication (with respect to performance), the prior art noise filters have not been economically efficient in reducing the undesirable effects of electromagnetic noise signals being generated by electrical and electromechanical devices.
More particularly, some conventional electromagnetic noise filters have heretofor been mounted within the housing of the electrical or electromechanical device from which an undesirable supply of noise signals is known to emanate. However, when the electrical or electromechanical device is an electric motor, or the like, the aforementioned interior location of the filter commonly causes the filter and its components to be undesirably susceptible to the adverse effects of heat produced during motor operation. Moreover, it has also been typical in other examples of the prior art for a filter capacitor to be rigidly affixed to an extension of the filter housing. By way of yet another prior art example, the capacitor has also been known to be rigidly molded into the motor vehicle wiring harness. However, and as a result of the aforementioned rigid capacitor placement, various stresses and strains to which the filter is subjected during handling and installation are transmitted to the capacitor. Hence, the capacitor has been known to fracture, thereby requiring that the filter unit be replaced and scrapped. What is even more, such damage to the capacitor could result in a short circuit thereof and a possible interruption in the operation of the electrical or electromechanical device as a result of a current overage and a corresponding rupture of the fuse associated with the device.
Accordingly, some electromagnetic noise filters have been provided with a fuse member that is adapted to rupture in the event that the filter is exposed to a relatively large current overage. However, because of the generally large size and corresponding inductance that are characteristic of the fuse member, the conventional noise filters have not been particularly suitable for applications wherein either relatively low fusing currents may be encountered or when high frequency performance (as in the FM or CB bands) is required.